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III. SLUG TEST DfETHODOLOGY • A. Testing Apparatus Each well was tested using a weighted section of PVC pipe, capped at both 'ends, and quickly lowered into the well completely below the static water level with a steel cable to produce an "instantaneous" rise in water level. Water level measurements were then recorded with time after the slug was submerged in order to calculate the transmissivity of the aquifer. Water levels were measur- ed using a Powers Well Sounder, which is essentially an electric cable with length markings and a weighted probe on the end which completes a circut as indicated by a volt meter at the surface when the probe reaches the water level in the well. A stop watch was started just as the slug entered the water. The falling water level versus time measurements continued until the water level in the well had equilibrated (returned to static) or, in the case of very slowly responding wells, until it was decided that sufficient data had been collected. If the well equilibrated within several hours after inserting the slug, the test was repeat- ed by quickly removing the slug and measuring the recovering water level with time. This recovery test provides a check on the data obtained from the initial, • or falling head test. Analysis methods are identical and equally valid for both falling head and recovery tests. The slugs used for testing were constructed out of 2.36 inch and 1.32 inch outside diameter PVC for use in 4 inch and 2 inch inside diameter wells respec- tively. Different slug sizes were used as indicated on the test data sheets for each well along with the calculated displacement volume (V) and water level change (Ho). The photographs of Figure III-1 show test apparatus with the cable spool mounted on the tail gate of a pick-up truck and the tripod and pully set-up over wells being tested. s ESA Geotechnical Consultants